Re: [PATCH 1/2] virtio_pci: Don't make an extra copy of cpu affinity mask

[Jakub Sitnicki <jakub@cloudflare.com>]

On Thu, Oct 19, 2023 at 08:55 PM +08, Xuan Zhuo wrote:
> On Thu, 19 Oct 2023 12:16:24 +0200, Jakub Sitnicki <jakub@cloudflare.com> wrote:
>> Since commit 19e226e8cc5d ("virtio: Make vp_set_vq_affinity() take a
>> mask.") it is actually not needed to have a local copy of the cpu mask.
>
>
> Could you give more info to prove this?
>
> If you are right, I think you should delete all code about msix_affinity_masks?

Sorry for the late reply. I've been away.

It looks that msix_affinity_masks became unused - intentionally - in
2015, after commit 210d150e1f5d ("virtio_pci: Clear stale cpumask when
setting irq affinity") [1].

Originally introduced in 2012 in commit 75a0a52be3c2 ("virtio: introduce
an API to set affinity for a virtqueue") [2]. As I understand, it was
meant to make it possible to set VQ affinity to more than once CPU.

Now that we can pass a CPU mask, listing all CPUs, to set_vq_affinity,
msix_affinity_masks seems to no longer have a purpose.

So, IMO, you're right. We can remove it.

Happy to do that in a follow up series.

That is - if you're okay with these two patches in the current form.

Thanks for reviewing.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=210d150e1f5da506875e376422ba31ead2d49621
[2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=75a0a52be3c27b58654fbed2c8f2ff401482b9a4